Hi,
Depending on the country you refer to as abroad, for Canada and The United Kingdom you'd need to achieve at least overall 7 bands out of 9 in IELTS, whereas, for Australia, New Zealand and The United States of America, you'd need overall 89+ score out of 120 for TOEFL.

Best Regards

Yes! You will mostly likely need a TEFL certificate to remain competitive in the ESL teaching market. Most Asian countries are hiring ESL teacher on a high demand. Having teaching experience isn't good enough to get yourself exposed in front of the big companies. A combination of advanced education and experience alongside certification will get you a stellar job as a ESL teacher.