UPDATE 2-Qatar to mark comeback with $12 billion international bond

(Updates with issue size, final book size, final price guidance)

DUBAI, April 12 (Reuters) - Qatar is set to raise $12 billion in its comeback to the international debt markets following a rift with its Gulf neighbours which started last year.

The Gulf state will mark its return with a triple-tranche U.S. dollar-denominated bond, a document from one of the banks leading the planned deal showed.

The issuance illustrates Qatar's access to international markets despite a boycott imposed by Saudi Arabia, the United Arab Emirates, Bahrain and Egypt, which severed diplomatic and transport ties with the country in June last year, accusing it of supporting terrorism. Doha denies the charges.

Orders of around $52 billion for the planned bonds are a sign of hefty demand for the bonds, which Qatar plans to price later on Thursday with maturities of five, 10 and 30 years.

Despite earlier concerns from some bankers and fund managers, Qatar's debt issuance was not complicated by Saudi Arabia's sale earlier this week of a jumbo $11 billion bond.

Some had thought the Saudi move may have absorbed demand from the market before the Qatari deal, forcing Qatar to offer higher yields to attract interest.

Philipp Good, chief executive at Fisch Asset Management, a Swiss firm managing more than $10 billion in assets, expected the Qatari debt offering to attract good demand.

"The initial price guidance of the Qatari deal is very similar to that of the Saudi deal. Comparing to on-the-run levels of the Qatari curve, the spread premium will attract decent demand," Good said.

Qatar gave initial price guidance earlier on Thursday, with the five-year tranche marketed at around 170 basis points (bps) over U.S. Treasuries, the 10-year at 200 bps over Treasuries and the 30-year at around 230 bps over.

It then tightened the guidance to final spreads of 135 bps over U.S. Treasuries for $3 billion in five-year notes, 170 bps over the benchmark for $3 billion in 10-year notes and to 205 bps over for $6 billion in 30-year paper.

Al Khaliji, Barclays, Crédit Agricole CIB, Credit Suisse, Deutsche Bank, Mizuho Securities, QNB Capital and Standard Chartered Bank are joint lead managers and joint bookrunners. (Reporting by Davide Barbuscia Additional reporting by Robert Hogg Editing by Larry King and Alexander Smith)