There is only one syllable in the word 'thought' but there are three phonemes, th, ough, and t. children are now taught phonemes at school but many, understandably, find it very difficult on meeting a new word to 'sound out' phonemes that then do not make a word sound they can recognise.
This is because of the irregularity of our language, unlike, say, Spanish, where sounding out phonemes would almost always result in the expected sound. Each of our phonemes holds a high risk of being portrayed differently in our spelling. Learning phonemes is very different for children learning than the seventies style of 'look and say' which relied on a child's visual memory for success.
The word thought is a long word, even though it is monosyllabic. It has three phonemes. The word contains two consonant diagraphs, th and ght, and a vowel digraph, ou, representing one sound each for a total of three sounds. Competency 001