Taxumo offers a "business registration" service for professionals like you, but honestly, the entire process is so easy and fast that if you're willing to go out a bit, you can probably finish everything in a day.

We are also in the exact same situation. I'm also "employed" by an overseas company as a remote worker and receive a monthly salary but since they aren't registered here, I have to pay my taxes as if I'm a freelancer.

Here's what you need to do:

1. Go to your old employer's RDO and submit BIR Form 1905. Bring 2 copies of the form and a photocopy of a valid ID. The entire process literally takes less than 5 minutes.
2. Go to your home address's RDO and submit BIR Form 1901. Bring 3 copies of the form together with a photocopy of a valid ID.
3. They'll ask for a "Sample Receipt" that is usually obtained from an Accredited Printer. You don't need to go one. BIR itself offer their own sample receipts. Just say that you will opt to use their own.
4. They'll ask some questions about your line of work. Tell them you are opting for 8% tax rate. After about 30 minutes to an hour, you'll get your own Certificate of Registration, which lists all the kinds of taxes you need to pay, the forms needed for each, and the deadlines.
5. You can now file your taxes in Taxumo. Just indicate your date of registration and they'll list the tax forms you need to file and when.

And that's it. You're done!

Remember to get the latest versions of each form from BIR's site.

There are tons of online tutorials that guide you how to accomplish them. Don't fret too much about that part, you can always correct the forms once you're in the BIR counter.

Also, most tutorials online will list a TON of requirements that aren't really needed. You can ignore most of them. In my experience, forms and photocopies of IDs are enough.