This suggests that if you already have an account in good standing with a SDFCU you may be denied. Did any of these people suggest why it was declined? May not have been a credit issue. What address do you have as your SDFCU account address? AFAIK, the closest that any bank card issuer came to having a global view on credit worthiness were those that subscribed to HSBC's 'global' account malarkey and moved around.
Does SDFCU allow an account with a Thai address? Most US banks, same as UK banks, want a domestic 'home' address. The only people that seem to get a break on domicile are those wishing to open 'wealth management' accounts with the likes of Citibank in Singapore where $200,000+ assures that you can live anywhere and not have to worry about credit checks.