Exactly. You will have to start an application and see what they ask for. But the Embassy website has the following information;
Non-Immigrant Type O (Retirement (pensioner aged 50 or above with a state pension who wants to stay in Thailand for no longer than 90 days) - single entry only)
Financial evidence e.g. A copy of pension statement if the applicant is a pensioner, or a copy of 1-month bank statement showing your income from pension, or 3-month bank statement of at least £10,000
Confirmation of legal residence in the UK or Ireland. Copy of health insurance that 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.