Thai is a tonal language with five tones — the same syllable means completely different things in different tones.
Mid (flat), Low (slightly falling), Falling (starts high, falls), High (starts mid, rises), Rising (low, dips, rises) — each tone is distinct and changes meaning.
The syllable 'mai' means five different things depending on tone: new, not, burn, silk, and the question particle — Thai children learn this; foreigners should too.
Mispronunciation causes confusion and sometimes laughter — but Thais are forgiving; context usually resolves meaning; trying is always appreciated.
Numbers and basic politeness phrases are worth learning with correct tones; for other words, show your phone screen with the Thai script rather than attempt pronunciation.
Google Translate's conversation mode and a basic Thai phrasebook app both help bridge tone gaps in real time — screenshots of Thai script work especially well for addresses and menu items.
Adding "krap" (male speakers) or "ka" (female speakers) at the end of a sentence signals politeness and softens any tonal mistakes — a small habit that goes a long way with locals.