The 39-year-old birdied the last three holes for a six-under-par 66 to sit just two shots off the lead in the Barclays Kenya Open at Muthaiga Golf Club in Nairobi.
Craig Lee also got off to a promising start with a bogey-free 67 in his first outing since losing his European Tour card in October while David Law was next best among five Scots on 71.
Doak’s first Challenge Tour round since last June contained seven birdies, transforming his day with a 2-3-4 finish to sit joint-seventh as South African Jaco Ahlers set a shot pace with his 64.
“I’ve got tonsillitis and going back to not speaking on a golf course is great,” said Doak, who held a full main Tour card for three seasons before losing that at the end of the 2015 campaign. “In a way it’s worked out well as I play my best when I’m in my own head, so it’s the silent assassin from now on.”
Lee was equally delighted with his effort, particularly as he hadn’t picked up a club in anger since the second round of the Portugal Masters, the final regular event on the European Tour last season.
The 39-year-old ended up losing his card by a single spot, leaving him unsure if he wants to continue as a Tour professional, but a flawless performance was certainly cause for encouragement.
“I’m very pleased with that,” admitted the Stirling man, who followed a birdie at the fifth by making further gains at the 10th, 12th and 14th. “I wasn’t expecting anything after having a lot of time off and it’s been hard to get back into it.
“I wasn’t sure what game was going to come with me this trip, so I’m delighted to see it is a pretty good one.”
Law, who birdied the last, is sitting tied for 73rd while Bradley Neil and Ross Kellett are both outside the top 100 after rounds of 73 and 75 respectively.
After signing for an eagle and six birdies, Ahlers leads by one from a five-strong group that includes Edinburgh-born Welshman Rhys Davies.