The guidance on the London website does not mention this, simply must be held in a Thai bank i take that as in one bank account, the Vancouver embassy states
A copy of bank statement (from Thailand financial institutes only) and a letter of guarantee from the bank with bank’s contact information showing a deposit of the amount equal to and not less than 3 Million bahts,
Which i read as it must be all in one account
further the London embassy website states
Applicants must have Thai medical insurance during their stay in Thailand (per the approval of the Office of Insurance Commission) and medical claims for outpatient must not be less than 40,000 Baht, for inpatient must not be less than 400,000 Baht. But then states 3 million baht coverage is required
Copy of evidence stating that applicants have insurance as per stipulated by the Office of Insurance Commission and health insurance of Thailand which covers COVID-19 related medical expenses, both inpatient and outpatient, no less than 100,000 USD for the whole period of your stay in Thailand. Please check < http://longstay.tgia.org> for more information regarding the insurance requirement.