Looked into it a bit, seems they may have stopped the direct taxis at Senai to Singapore a number of years back (essentially, the driver must be licensed for it & have their passport on hand to go through immigration).

You can try calling the taxi desk at Senai (though who knows if they will pick up), or organise a prepaid taxi in advance.

The alternative is to go from JHB to Larkin terminal, then get a SG-plated taxi (Comfort Delgro / SMRT / whatever) to take you to your final destination (or at Larkin pay a MY-plated taxi the standard fare to Queen Street in SG + take a local taxi to your final destination).

https://www.tripadvisor.com.sg/ShowT....html#89192413


Note, it appears they’re only letting a few taxis do the cross-border route right now:
https://www.straitstimes.com/singapo...-jb-from-may-1


Another good resource (not sure who owns or manages it, but has info well organised): https://www.taxisingapore.com/singapore-to-johor-bahru/