TL;DR:Possibly — but only if the insurer’s policy, underwriting and waiting‑period rules allow it; many policies exclude or limit pre‑existing chronic conditions unless declared and accepted.
Coverage for a chronic condition depends on the type of plan, the insurer’s underwriting rules and whether the condition existed before you bought the policy. If you’re a foreigner in Thailand: public schemes (Social Security) cover employed foreigners for work‑related and some general care but don’t guarantee full chronic‑disease management; private and international plans vary. Typical patterns: pre‑existing conditions are often excluded or subject to a waiting period (6–24 months); insurers may accept you with a premium loading or limit benefits for that condition; travel insurance usually excludes ongoing chronic illnesses unless declared and accepted. To know for sure, check the policy schedule and wording (definitions of “pre‑existing”, waiting periods, chronic disease clauses), give full medical disclosure, and obtain written confirmation of any acceptance or exclusion. If you want, provide the insurer and policy name and I’ll review the specific wording. (Sources: Thailand Office of the Insurance Commission consumer guidance; Social Security Office; major private insurers’ pre‑existing conditions pages.)
Answer will be updated soon