Going from Thai to Cantonese (粡θͺ) has a composite linguistic distance of 67% (heuristic estimate). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Thai β Chinese
Tai-Kadai β Sino-Tibetan
The 5 languages with the lowest linguistic distance from Thai:
A quick 3-question check between Thai and Cantonese. No signup.