The crimes of an Adelaide sex tourist are the most serious case of sex offending in Australia, a court has heard.

Ruecha Tokputza, 31, appeared in the district court on Wednesday after pleading guilty to 51 charges against 13 babies and boys over more than six years.

He groomed children for sex in Australia and Thailand, filmed their abuse and shared it online.

The prosecutor Heath Barklay SC told the court his office could not find an Australian sex offences case as serious as Tokputza’s, and asked the judge, Liesl Chapman, to sentence him accordingly.

Barklay said Tokputza’s crimes were more serious than those of the notorious Families SA paedophile Shannon McCoole, who was sentenced to 35 years in jail in 2015.

He said a major difference between the pair was McCoole’s remorse, which he showed through a letter of apology to his victims.

“When one contrasts the two in that way, in my submission, this matter is plainly much more serious,” Barklay said. “It’s for that reason that there is a limit to the use of the McCoole matter in this case.”

McCoole also committed fewer crimes – 20 offences against seven victims over the span of more than three years.

Chapman will sentence Tokputza in May.