install libthai4r

install_libthai4r.sh

#!/bin/bash
sudo apt-get update && sudo apt-get upgrade -y
sudo apt-get install -y libdatrie-dev libthai-dev

cd /tmp
mkdir libthai4r && curl -L https://github.com/ptantiku/libthai4r/tarball/master | tar xz --strip 1 -C libthai4r
cd libthai4r
ruby extconf.rb
make
sudo make install

# optional: test thai word break
# ruby test/thbrk.rb
# expected: ภาษา|ไทย|เป็น|ภาษา|ที่|ง่าย|ที่สุด|ใน|โลก

My output of ruby extconf.rb:

checking for package libthai >= 0.1.1 ... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/usr/bin/$(RUBY_BASE_NAME)2.3

Output of dpkg -l |grep libdatrie:

ii  libdatrie-dev:amd64                  0.2.10-2                                 amd64        Development files for double-array trie library
ii  libdatrie1:amd64                     0.2.10-2                                 amd64        Double-array trie library

Output of dpkg -l |grep libthai:

ii  libthai-data                         0.1.24-2                                 all          Data files for Thai language support library
ii  libthai-dev:amd64                    0.1.24-2                                 amd64        Development files for Thai language support library
ii  libthai0:amd64                       0.1.24-2                                 amd64        Thai language support library