Not sure when this began, sometime within the last 30 days, but now when you enter Building B at The Government Complex there is an officer who scans your passport with a computer before you go through the metal detector, instead of signing in the book. Thai citizens show their National I.D. Card.
TLDR : Answer Summary
Recently, the entry procedure at Building B of The Government Complex has changed. Now, officers scan the passports of foreigners before passing through the metal detector, a procedure that some users note was not in place for them during earlier visits. Some commenters reported never having to sign in or show their passports at all. The discussion raises concerns about what to do if a foreigner does not have their passport with them, with suggestions that a photo ID might suffice.