When the suspicious document appeared not to list the correct certification, Lal was required by WorkSafe to be supervised.
Despite this, Lal again supplied a second phony certificate in December 2017.
WorkSafe then interviewed Lal in February 2018 and he confessed to using altered certificates of two other employees.
He claimed he did so because of pressure from his manager to complete the required training courses.
After being prosecuted this year, Lal was convicted and given a 10-month home detention term in August after pleading guilty to two charges of using forged documents to obtain pecuniary advantage.
Judge David Harvey considered Lal's offending had serious health and safety implications, while the continued deceit of his employer had "aspects of corrupt practice".
But Lal appealed to the High Court this month, arguing "the sentence is wrong in principle as rehabilitation was not given enough weight".
However, in his decision released last week, Justice Pheroze Jagose continued Judge Harvey's theme.
Lal was "flagrantly dishonest", Justice Jagose said.
"His motivation to satisfy his manager, and to retain his employment, does not justify such duplicity, which was to permit him to continue to conduct regulated activities in breach of statute," he added.
"Mr Lal's offending had a measure of sophistication about it, as even [the] issuing agency initially believed the certificate genuine. It involved a serious breach of his employer's trust. It was aimed at avoiding health and safety objectives, which by their nature are to be taken seriously and depend for their integrity on a unitary whole."
While the offending was discovered before any consequences arose, Justice Jagose said, they could have been "catastrophic" for Lal, his employer, and others.
He dismissed the appeal.
WorkSafe's general manager for high hazards and energy safety, Tony Hetherington, said after Lal's sentencing there were potentially serious consequences for his offending.
"The certification process is important because handling the chemicals covered by the requirements presents significant risks to the handler, people working nearby and potentially others who may have to respond in an emergency," he said.
"The certification process is part of ensuring these risks are properly managed, so people such as Lal who try to sidestep the requirements are putting themselves and others at risk."