I sympathise with this problem greatly. I was frustrated at how slow my Mandarin Chinese reading speed was compared to my English. Yet even my Mandarin Chinese speed was much faster than when I started reading Tamil in script: Excruciatingly slowly.
The first thing to keep in mind is that reading is not a skill like walking or breathing: It doesn’t come naturally to us. It requires practice, lots of deliberate practice, before it becomes automatic. It’s best to keep in mind that you once read in a slower speed for English, even if you do not realise it. Reading speed will come, but it will take time.
General Tips for Reading Speed
I think you should try to read with English transliteration first to get a sense of vocabulary and grammar. Only once you understand the basics of each should you then proceed to reading in script. Reading in script directly early on will be difficult to process because you won’t have the vocabulary to attach to each word you read out.
When it comes to script, I find the best way of improve reading speed is to do a combination of reading more, transcribing words and sentences through typing or writing, and reading out loud with a teacher. Reading more makes sense, but the latter two may require some explanation.
Transcribing words and sentences forces you to think about the character/word you’re typing if the language is in a different script. What does each character in தமிழ் sound like? What is the sound of the characters 下雨? Attempting to process each character/word as accurately and quickly as you can helps automate reading skill. If you forget a character/word, attempt to remember the sound as best you can before checking a dictionary or using Google Translate to help with sound recall.
Reading out loud with a teacher is especially helpful when you’re just starting to read or even at an intermediate level. You get feedback about whether you’re reading everything correctly, and you can ask questions as to why this letter or character sounds the way it does.
You WILL feel tired or exhausted after a certain amount of time. Try and stop before you get too tired to keep your motivation levels up.
Reading Tips for Singaporean Mother Tongue Languages
For a language like Malay, this isn’t too bad since it uses the alphabet we’re familiar with in English. Getting familiar with the affixes, such as understanding what “Men-” or “Ber-” do to the words they’re attached to, will help with comprehension. Once that happens, it’s a matter of making reading more automatic.
For a language like Tamil, it’s more difficult because it uses a different script. Start by reading singular words, preferably shorter ones, but if you run into a long word, try reading as much as you can. I highly recommend reading with a teacher when you first start out so that you can be sure you’re reading the words correctly. This is especially important as some Tamil letters differ in sound depending on where the letter’s found (for the technically inclined: there’s differences between voiced and unvoiced consonants depending on phoneme position, whether it’s Beginning, Medial, or Final).
For a language like Mandarin Chinese, you might have even more difficulty with reading and memorising the sounds of each character. You’ll need to know how to read hanyu pinyin. I recommend finding texts or books with pinyin above or below each character. Readibu is a great resource for reading because you can read native language texts with pinyin annotation!
Conclusion
Read in English Transliteration, then read more in script, and make it faster with transcription and reading out loud! Do remember to take reading in small bits and try to stop before you tire out so that you’ll feel motivated to keep on going later or after a day or two.