Three things about Thai are worth knowing before your first phrase, because each of them changes how you should study.
The same syllable said at five different pitches is five different words. ไม่ (mâi) is not, and ไม้ (mái) is wood. This is why listening matters more than reading at the start, and why a wrong tone is not a small accent problem: it is a different word.
Thai script is not an obstacle to speaking, and you do not need it to start. But romanisation is a crutch that stops working: if it never goes away, you never learn to read. The control in the header lets you set transliteration to always, on tap, or never. Start on always. Move to on tap when you begin recognising letters.
No verb conjugation. No plurals. No articles. No tenses in the European sense. Word order does most of the work, and politeness is handled by a particle at the end of the sentence.
You will not understand the reply. That is not a sign you are behind — it is the normal first six months, and the people who keep going are the ones who have a comfortable way to say so. Three sentences carry an astonishing amount of weight:
Four tracks run in parallel on this site, and they are meant to be used together rather than finished one at a time. This is the order that works.
Hard in two places and unusually easy in a third, which is why the answers you read contradict each other. The two hard parts are the tones and the script, and they are hard in different ways: the tones are hard to hear and to produce reliably under pressure, while the script is merely a lot to learn — a few weeks of daily work, with no conceptual difficulty in it once the tone rules make sense. The easy part is the grammar, and it is easier than almost any European language: nothing agrees with anything, verbs never change, and a sentence you build out of dictionary forms is usually correct.
Four specific things trip up English speakers, and they are worth naming so you recognise them as they happen. Vowel length changes meaning, so a short vowel and a long one are two words rather than two accents. Thai distinguishes sounds English treats as one, which is why this site writes ป (bp) and ต (dt) — they sit between the English pairs rather than on either side. Thai writes no spaces between words, so a sentence arrives as one unbroken run of letters. And you cannot look up a word you have only heard, because you need the spelling to find it, which is the real argument for learning to read earlier than feels comfortable.
Against another language: the US Foreign Service Institute, which is the only organisation that has systematically timed this for English speakers, groups Thai with the hard-but-not-hardest languages at roughly 1,100 class hours, and puts Japanese, Chinese, Korean and Arabic in a harder group at about double that. So Thai is easier than Japanese by the only measure anyone has, and considerably harder than Spanish. Those hours assume full-time study with a teacher; they are a ranking, not a timetable for your evenings.
Useful milestones, assuming twenty to thirty minutes a day and living in Thailand, where you get free practice every time you buy something:
Twenty minutes daily beats three hours on Sunday, and it is not close. Tones and letters are recall problems, and recall is built by frequency rather than duration.
Most of it, yes. Vocabulary, grammar, reading and listening are all things you can do alone, and this site is built on the assumption that you will. The exception is your own tones, and it is a real exception: you cannot hear your own errors, because the mistake is precisely that your ear is not yet making the distinction. Left alone, most self-taught learners spend a year confidently saying words that are not the words they mean.
The fix is small and it is not a course. Record yourself saying a phrase, play it against the audio here, and notice you cannot tell them apart yet — that is the point at which you know what to work on. Then find one person who will correct you: an hour a week with a tutor, or a Thai friend who is told explicitly that you want to be corrected, because otherwise they will politely understand you anyway and you will learn nothing. Everything else on this site you can do on your own.
Use the transliteration control in the header as a ladder rather than a setting. Start on always, so every phrase shows its romanisation. Once a few letters start looking familiar, move to on tap — the Thai shows, and the romanisation appears only when you ask for it, which turns every card into a small test instead of a small reading. Move to never when you can go a whole page without reaching for it. People who stay on always for a year can speak and still cannot read a sign; the ladder is what stops that happening.