Regular visitors to Bangkok would be aware that 'anything' can be purchased in Bangkok. Fake ID's including FBI, Secret Service, drivers licences for any Countries etc etc. Stolen Passports in Thailand are valueable and are modified as required with a new picture.
There are many fake passports in Malaysia sourced from Thailand due to the passport rules there. If you lose a passport in Malaysia it is a serious matter and you have to wait a period of time for a replacement. If you lose the replacement you may be ineligible for a further issue for up to 5 years.
Malaysia also has a Passport Blacklist with a target update of less than 1 hour after receiving notification from a Government Agency or Court. You are added to the Blacklist. You can be denied leaving Malaysia if you become Bankrupt, have an upcoming or current Court Case, owe Income Tax, been convicted of a Criminal Offence and numerous other reasons, hence travel on fake Passports.
Readers may also be surprised to hear the critical parts of some Passports including US Passports are made in Thailand, a Country with a radical Islamic population.
It will be interesting to see what is said about the 'impersonators' on MH370. I hope they could turn out to be Malaysian businessmen.