Learning Thai is easy for Indians because of following reasons
Thai uses Sanskrit derived words as its formal spelling.
Some other words are derived from Pali, which is a form of Sanskrit itself (to say practically).
Thai writing system is just another form of Brahmic Writing system which is used throughout India in our various scripts from Tamil to Kashmiri and from Gujrati to Assamese and of course Devanagari script. This brings a lot more ease for Indians. Also you may be interested in : Meaning of name Rochak रोचक नाम का अर्थ
Thai psychological concepts conform to Buddhist concepts which in turn took birth in India so their psychological terminology is also related to India, so it is helpful to learn Thai reactions on various occasions.
Hope this helps you to understand why learning Thai is easy for Indians, and why Indians do not easily feel this fact.