No needs to be in one savings account and 3 months or better 6 months of statements, some Thai embassies might be flexible but the important balance in 500,000 THB or equivalent currency showing as the latest balance. Contact the Thai Embassy/consulate for guidance
Just remember to enter your DTV No in the box “Visa” on the online tdac form (only use the official one, it’s free) every foreigner has to compete this online and submit up to 3 days before arrival into Thailand.
Again on this form you can either leave blank your exit travel date or put the date down if you know the date your are departing Thailand.