If and when: thâa and mêua

Start with the word that actually causes trouble in ถ้า (thâa) sentences, because it is not ถ้า. It is the little ก็ (gâw) sitting in the second half. Every dictionary glosses ก็ as "also", so learners read ถ้าฝนตก ผมก็ไม่ไป as "if it rains, I also will not go" and wonder who else is staying home. In a conditional, ก็ does not mean "also". It means "then, in that case", and it is the hinge that ties the result back to the condition. English marks the condition ("if") and leaves the result bare; Thai marks both ends. The everyday frame is: ถ้า + condition, then subject + ก็ + result. ก็ stands right after the subject of the result clause and before everything else (จะ, ไม่, the verb): ถ้าฝนตก ผมก็ไม่ไป (thâa fǒn dtòk phǒm gâw mâi bpai). When the subject is dropped, which is normal Thai, ก็ opens the result on its own: ถ้าลดได้ ก็เอาสองตัว. You can leave ก็ out of short, punchy sentences and still be understood, but real speech keeps it in far more often than not, because without ก็ the two halves sound like separate statements instead of one thought. The one systematic exception: when the second half is a request or a question rather than a statement of what follows, Thai drops the hinge, which is why a ขอ... or ...ได้ไหม sentence after a ถ้า clause carries no ก็. If you fix a single habit this month, make it saying gâw at the join. ถ้า carries no tense and needs none. ถ้าฝนตก covers "if it rains", "if it rained" and "if it is raining" alike; context does the rest. There is no "would" for the result either: where English says "I would not go", Thai just says ไม่ไป, adding จะ (jà) only when the result is a plan: ผมก็จะไม่ไป. Condition first, result second is the default order, the same order as an English "if" sentence, so the only genuinely new mechanics here are ก็ and the absence of tense. That is why this pattern is usable within days, not months. One refinement completes the picture: คง (khong). When the result is a guess or a would-be outcome rather than a plan, Thai hedges it with คง or คงจะ, "probably, would": ถ้าไม่รีบ ก็คงไม่ทัน (thâa mâi rîip gâw khong mâi than), if we don't hurry, we probably won't make it. The same little word does all the work English does with "would have": ถ้ารู้ก่อน ผมก็คงไม่มา (thâa rúu gàwn phǒm gâw khong mâi maa), if I had known, I would not have come. Nothing in the ถ้า clause changes; whether the sentence is real, unlikely or contrary to fact lives entirely in คง and context. That is the whole of Thai's "would" machinery, and it is one syllable. Now the conditions you will actually say. At a market, ถ้าเกินห้าร้อย ก็ไม่เอา (thâa goen hâa ráwy gâw mâi ao) is a complete bargaining position: name the ceiling, refuse past it. ไม่เอา, literally "not take", is the standard soft walk-away, firmer than silence but not rude. At a guesthouse, ถ้าห้องไม่ว่าง (if the room is not free) sets up the ask for a different room or a different night without any drama. These sentences work precisely because ถ้า...ก็ states a condition without accusing anyone of anything: you are describing a world, not criticising a person. "When" is where the second confusion lives, because Thai splits English "when" into several words and the textbook one is the one you will use least. เมื่อ (mêua) is correct but formal: signs, announcements, the news. In everyday speech, ตอน (dtawn) marks a time slot, ตอนที่ (dtawn thîi) plus a clause marks a specific occasion (usually past), เวลา (wee-laa) means "whenever, when in general", and พอ (phaw) ... ก็ means "as soon as". Asking "when?" is เมื่อไหร่ (mêua-rài). It sits at the end of the question; move it to the front only when you mean to sound fed up. Use เมื่อ for everything and you will be understood, but you will sound like the evening news reading its own weather report. The everyday เมื่อ compounds are a small closed set, so learn them as plain vocabulary: เมื่อไหร่ (mêua-rài) "when?", เมื่อกี้ (mêua-gîi) "just now", เมื่อคืน (mêua-kheun) "last night", เมื่อวาน (mêua-waan) "yesterday", เมื่อวานซืน (mêua-waan-seun) "the day before yesterday", เมื่อก่อน (mêua-gàwn) "before, in the past". Notice they all point backwards except the question word: bare เมื่อ compounds are how spoken Thai reaches into the past. Clause-เมื่อ you mostly meet in writing: เมื่อเอกสารครบ ก็ยื่นได้เลย is exactly what the notice at an immigration counter says. Notice the ก็ again. Time clauses take the same hinge as ถ้า clauses, and that is the deeper pattern worth internalising: whenever a clause comes first (a condition, a time, a topic), ก็ picks up the thread in the second half. One mechanism, many sentence types. ตอน also carves up the day: ตอนเช้า (dtawn cháo) in the morning, ตอนบ่าย (dtawn bàai) in the afternoon, ตอนเย็น (dtawn yen) in the evening, ตอนกลางคืน (dtawn glaang-kheun) at night. For an occasion, use ตอนที่ plus a clause: ตอนที่ผมอยู่ที่นี่ปีแรก, "when I lived here my first year". For future arrangements, plain ตอน plus a slot is all you need: เจอกันตอนเย็น, see you this evening. No preposition, no tense, just the slot. เผื่อ (phèua) is "in case": you act now to cover a possibility later. เอาร่มไปด้วยเผื่อฝนตก, take an umbrella along in case it rains. Keep it distinct from ถ้า: a ถ้า sentence waits for the condition to happen, a เผื่อ sentence hedges before it happens. เผื่อ has a second everyday job, "for someone absent, on someone's behalf": ซื้อเผื่อผมด้วยนะ, buy some for me too, said as a friend heads out to the shop. Both jobs are the same idea, making provision for something not in front of you yet, which is why Thai is happy to use one word for both. ไม่งั้น (mâi-ngán) is "otherwise", the compressed spoken form of ไม่อย่างนั้น (mâi yàang nán), literally "if not like that". It follows advice or an instruction and names the consequence: รีบหน่อย ไม่งั้นไม่ทันรถ, hurry up, otherwise we will miss the bus. Under the hood it is a folded-up ถ้า clause, which is why it needs no ก็ of its own. Bare งั้น (ngán) also stands alone as "in that case, then": งั้นไปกันเลย (ngán bpai gan loei), "then let's just go", the word for the exact moment plans change. Finally, the whole if-family, so nothing ambushes you later: everyday ถ้า; colloquial ถ้าเกิด (thâa-gòet), literally "if it arises", favoured for unwelcome surprises; formal ถ้าหาก (thâa-hàak) and bare หาก (hàak) on signs and in announcements; สมมติว่า (sǒm-mút wâa) "supposing that" for hypotheticals; เผื่อ for hedging; ไม่งั้น for consequences. ถ้าหาก and เผื่อ can optionally add ว่า (wâa) with no change in meaning. One cousin belongs here because it runs on the same hinge: ถึง (thěung) ... ก็ means "even if": ถึงฝนตก ผมก็ไป (thěung fǒn dtòk phǒm gâw bpai), even if it rains, I'm still going. Same shape as ถ้า, opposite promise: ถ้า makes the result depend on the condition, ถึง...ก็ says the result survives it. And when you reach for English "unless", do not hunt for a word: Thai says it as ถ้า...ไม่, "if not": ถ้าฝนไม่หยุด ก็ไม่ต้องไป, unless the rain stops, no need to go. That is the entire set. There is no subjunctive, no verb agreement; the only "would" machinery is คง (khong), which you already met. Rain, room and price are all the same sentence shape, and you already have it.