London to Beijing RTN then a Separate Beijing to Bangkok RTN

Hi,

Can I buy a London to BJ Return Leave London 2nd April and Return 14th April. I also purchase in the UK a BJ to Bangkok Rtn ticket leaving BJ in 7th April and returning on the 11th April.

Can I get the 144 hr Visa twice?

Also does the ticket I purchase have to be a through ticket or can it be as I describe and you just show immigration your ticket to leave BJ?