Windows service runs as 64 bit when ran as domain account

Question

I have created a windows service and compiled on 32 bit.

I deployed the service on 64 bit machine.

Now, when I run the service as local system account it runs as 32 bit while if I change it to run as domain/network account it starts as 64 bit service.

Can anyone please help me on what should I do so that it always runs as 32 bit??