The board of directors resolved to appoint Sigve Brekke, a vice-chairman, to act as the interim CEO, the company told the Stock Exchange of Thailand on Tuesday.
Mr Brekke, also executive vice-president and head of the Telenor Asia operations, was co-CEO of Dtac in 2002-05 and CEO in 2005-08.
Mr Abdullah was appointed Dtac's CEO on March 1, 2011. Prior to that, he was CEO of Telenor Pakistan in 2008. From 2002-07, he was chief technology officer of DiGi Telecom.