Trades Recognition Australia considers TESDA as the governing body for technical or vocational trades in the Philippines. There are 2 parts in assessing his occupation, first would be the qualification then the work experience, he should check training.gov.au if the subjects he had in school coincides with the course in Australia. I did a quick search and below is the training qualification needed and the occupation in the SOL list.
OCCUPATION: WELDER (FIRST CLASS) – ANZSCO Code: 322313
QUALIFICATION: MEM30305 CERTIFICATE III IN ENGINEERING
(FABRICATION TRADE)