My friend is in Thailand and is from the Uk,he has a multiple entry 1 year non immigrant visa.next year when he returns to the Uk when he applies for his new multiple entry 1 year visa his passport will expire before he has used all the entries.So does he then apply at the British Embassy for a new passport and when he leaves to cross the border and re-enter Thailand just show the old Passport and the new one at the same time.Will this cause a problem with immigration ?

Thanx.

He will not obtain such a visa next year without a new passport first.

He should apply for a new passport before he applies for the visa

From the UKPA web site

You can renew your passport whenever you want and do not have to wait till your passport is expired to renew it.

However, we can add no more than nine months unexpired time from the old passport to the new one.