Hear Thai consonants and vowel length
Listen for a puff of air and the difference between short and long vowels.
A puff of air can matter
Thai distinguishes plain and aspirated stops: an aspirated consonant has a puff of air. In the course’s reading hints, kh, th and ph describe that puff, not separate k+h, t+h or p+h syllables. th does not mean English “th”, and ph does not mean f. Listen to crow, with plain k, and leg, with a puff of air.

กา
crow
ขา
legShort and long are different vowels
Vowel length can distinguish words. Keep a long vowel audible instead of shortening it to match English habits. Listen to look and scold: both length and tone differ, so it is a first listening encounter, not a pure length-only test.
ดู
lookดุ
scoldThe end of a syllable has its own rules
A consonant can have a different sound at the end of a syllable. Final stops close without an extra vowel or a strong released puff. You will practise these endings before using them in tone calculations.