Tha - WAS 
For gender - Masculine 

Past tense to IS 

English - He was a driver. 
Hindi - Woh driver tha. 

The same word would be 'THI' if the context is feminine 

English - She was a driver. 
Hindi - Woh driver thi. 
thi and tha both are past tense but thi infemine and tha in masculine
Ok sarayu i will make u understand the difference. the meaning of thi is used for a female for example vah ladki abhi padhai kar rahi thi. and tha is used for the male person for example vah ladka vaha khel raha tha.and the similiarity between both is that they both are in the past tense.
hope this helps u sarayu !!!!!!!!!
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