No Thai voice found on this device, so audio elsewhere plays the romanized pronunciation instead (Quiz and Flashcards stay silent until the answer is revealed, so it doesn't give it away). To hear real Thai audio, install a Thai language/speech pack: Windows Settings → Time & Language → Language & region → Add a language → Thai (enable the speech pack when prompted).
A syllable's final consonant sound (ตัวสะกด) determines whether it's a live syllable (คำเป็น — ends in a sonorant: -ng/-n/-m/-y/-w) or a dead syllable (คำตาย — ends in a stop: -k/-t/-p). Several consonants share the same final sound even though they sound different at the start of a syllable.