china visa for a canadian in thailand

hi, i need an entry permit for PRC but im confused im leaving canada for a world tour on january 21st but only arrive in PRC on may 26th i cant do the application for entry permit back home since it will be more than 3 months until we get there so we thought about doing our application in bangkok we need a valid entry permit for 37 days and at least 2 entries because we are staying from may 26th to june 20th then we go to japan for a month and return to PRC july 20th to july 30th also if we have proof of all our accomodation in PRC do we need the invitation letter if yes where can i get that?

Thanks