Bangladesh coach admits 'uncertainty' prompted bowling first in Test
Captain Mominul Haque decided to send South Africa in on a well-grassed pitch after winning the toss.
However, half-centuries by skipper Dean Elgar (67) and Temba Bavuma (53 not out) enabled South Africa to finish the first day with a slight advantage on 233 for four.
"Bangladesh are trying to find and improve their Test match cricket," said Domingo, a former South Africa head coach.
"There is still some uncertainty regarding batting on wickets that maybe offer a little bit of pace and bounce. It's something we're trying to address as a coaching team, to have the confidence that when it is tough and tricky to maybe be willing to front up and bat."
Domingo said statistics over the past 10 years only slightly favoured batting first. He said a green pitch and early cloud cover were factors in favour of Thursday's decision.
He admitted that Bangladesh bowled poorly in conceding 60 runs in 13 overs in the first hour at the start of a 113-run opening partnership between South African captain Elgar and Sarel Erwee, who made 41.
"It's a very inexperienced bowling attack," said Domingo.
"They were obviously a bit nervous and maybe excited and too eager to bowl on a wicket they thought would help them. But they were superb after lunch."
South Africa were 95 for no wicket at lunch but could add only 70 runs in 28 overs for the loss of three wickets between lunch and tea.
Bavuma and Kyle Verreynne steadied the innings with an unbeaten fifth wicket partnership of 53.
Bavuma, playing in his 50th Test, made 53 not out and Verreynne was unbeaten on 27.
Outstanding Mehidy
Off-spinner Mehidy Hasan bowled 26 overs, taking one for 57. He enabled Mominul to rotate his fast bowlers in short spells.
Mehidy's outstanding contribution of the day, however, was a sensational run-out, diving to stop a cover drive by Bavuma and throwing down the stumps from a kneeling position to dismiss Keegan Petersen.
Elgar was the only victim of a delivery which behaved unpredictably, gloving a catch to wicketkeeper Liton Das off a Khaled Ahmed ball which lifted sharply off a good length.
South Africa, missing five players who chose to play in the Indian Premier League, fielded two new caps in left-handed batsman Ryan Rickelton and fast bowler Lizaad Williams.
Rickelton looked solid before playing an ill-judged pull shot against Ebadot Hossain and spooning a catch to mid-on.
Rickelton said he was surprised Bangladesh chose to bowl and that South Africa were happy to be bowling second because they had picked two spin bowlers on a pitch they expected to turn later in the match.
Off-spinner Simon Harmer returned to Test cricket after a six-year absence during which he has starred for Essex in English county cricket.
Bangladesh were without opening batsman Tamim Iqbal because of illness and left-arm fast bowler Shoriful Islam was ruled out because of an ankle injury.
Domingo said Bangladesh could not risk Shoriful after they decided to pick an extra batsman, leaving them with only four front-line bowlers in the absence of all-rounder Shakib Al Hasan, who has returned to Bangladesh because of family illness.
The start was delayed by 35 minutes after sightscreen malfunctions at both ends, with ground staff struggling to cover both screens with white cloth.
The umpires decided to move back the playing times by half an hour but it was not possible to complete a full day's play at South Africa's most easterly Test ground where bad light is often a problem.