I want to buy a phone and few other things, the 10% off code I had last week is seemingly expired already.....

go to lazada and click the sign up for newsletter and promotions and enter your email

(they will spam you to death after this with coupons and codes for allsorts)

They appear to have three discount codes most days.

One will give you 80 baht off your purchase.

The other two give a percentage discount dependent upon the value of the purchase...however, the higher discounts are now generally only available to purchases made through the Lazada App., (discriminating against buyers like myself who use a PC rather than a Smart Phone)

As speedtriplers says, if you subscribe to emails, you will get at least one a day which, when you click on, will take you to the Lazada web site and a pop-up will show the days discount codes.

Edit. Just tried it and no discount codes showing at present...