Does the invitation for a Non-O visa need to be handwritten and in Thai?

The invitation letter for a Non O visa does not necessarily have to be handwritten or in Thai. It can be a simple typed letter in English, as long as it clearly states the invitation and includes relevant details. It's advisable to also include identification examples, like a Thai ID and marriage certificate, especially when applying from overseas. Some commenters suggested that letters could be written in the husband's home language if applying from abroad.