Can I extend my visa exemption entry in Thailand for my Hong Kong passport?

HongKong passport = China passport

Hong Kong is treated the same as China in Thailand. If you had applied for British Passport before 1997 or your parents had then no problem.

Go HK or elsewhere to apply for a 60day tourist visa. Only this one can extend for another 30day, and/or to proceed for non-O.

Unfortunately you did not enter “visa exempt” on a Hong Kong passport. You entered under the visa waiver scheme based on a bilateral agreement. They’ve been upped to 45 days now but you got 30 when you arrived (before Oct 1st).

These entries cannot be extended like a visa exempt entry can.

The 7 days you were offered is in actual fact a denial to approve an extension and they give you 7 days to leave.