Laos and Cambodia are good options but note Cambodia can take up to a month for approval. Laos is around 10 -15 business days. Indonesia is another great option. You do not need a law firm to submit your application. You can look thru the threads and find everything you need for a successful application yourself., You can apply as a freelancer, without registration for yourself. Submitting the business registration of the company you work for will strengthen your application. 3 months invoices with the client should be suffice, provide a cover letter detailing that is how long you have worked for them.