Which blood group is more prone to typhoid?

No such a thing: Typhoid is an infection caused by bacteria called salmonella sp. Personal hygiene is very important- as this disease can be spread easily through contaminated food and water. This is an infectious disease and there is no correlation between any specific blood type with susceptibility to thyphoid infection.

None: This theory was floated back in 1954 but has never gained ground in any scientific circles. This is a false idea that type o is most at risk & not been born out. Interestingly--& really against the ideas of the "blood typists" small studies have actually shown slight increase in rotovirus risk to type a & ab, & complex portions of blood typing to norovirus & h pylori, but none to typhoid. Sorry.