If the account is 0 for more than a year, its closed automatically.
You need to open a new one , requirements here -
Document required for Foreigners -
Passport
Visa (non-immigrant VISA) or identification documents issued by the government of the country of the nationality such as national ID card, driver’s license, House Registration, etc.
Documents per the objectives of entering Thailand :
- Work in Thailand : Documents showing permission to work in Thailand, such as Work Permit
- Retirement in Thailand : Proof of address in Thailand such as house / condominium rent contract, water / electricity bill, etc.
- Study in Thailand : Certification letter issued by school or educational institution.
https://www.kasikornbank.com/en/personal/account/pages/savings.aspx