Actually, April International is an insurance broker and not an insurance company. April does not seem to have an insurance broker's license in Thailand. Instead, it looks like it has an assistance company here for the purpose of coordinating claims with hospitals.
April International's website directs inquiries for quotes for Thailand to a page that states that policies are issued by LMG Public Company Ltd. If the OP has had an LMG Thailand policy for the past five years, then he may benefit from the 5-year time bar.
The OP may have engaged April International in France, or perhaps somewhere else outside Thailand, and gotten an offshore policy, but he does not state that in his post. Lacking that specificity, I would suspect that April International routed his request to LMG and his policy is actually issued by LMG Thailand.
And as an aside, LMG has just this month announced that they are selling their operations in Thailand and Vietnam to Chubb.