(Edit to change thread title as it has evolved from my original enquiry and there are lots of knowledgeable folk here to help out)

Original Post

Flying in from SIN and connecting to Sandakan, both sectors MH. BA Silver card holder. Long stop over between flights.

Usually I go straight to immigration at the transfer to the domestic air side area and then use the Domestic Golden Lounge.

Can I delay this and use the Regional Golden Lounge before clearing immigration? (It has an omelette station in the morning!)