personally I hope they keep the mandatory insurance, not necessarily for covid but general insurance to cover you. Should be mandatory worldwide in my opinion.
Speak to Thai Embassy in India, whichever is closest to your mother. They'll advise her and provide a list of documents she'll need to provide in order to apply for a new visa and COE.
If she gets back to Thailand and has to do quarantine then it has to be done at an approved hotel, at her or your expense, and not at your place.