I've heard that some countries may require some travel insurance proof when entering to the country.
Which countries require that and what kind of insurance?
Do they accept any standard travel insurance such as that included with some Credit Cards, VISAs or personal banking although there is no any proof or some more specific certificates or papers (e.g. for Malaria)?
Specifically I'm interested for Hong Kong, Vietnam, Singapore, Philippines, Malaysia and Thailand.
Similar question, but for Europe.